Miniaturization and diversification of semiconductor devices become more advancing than ever. In this connection, producing methods of the semiconductor devices are diversified with respect to each device structure and production step. Taking etching of a substrate as an example, a variety of chemical species, processing conditions, and the like are proposed in accordance with both kind and structure of a substrate material in both dry etching and wet etching. Further, intensive research and development are proceeding with the etching.
Among them, a technique of precisely etching to form a device structure of CMOS, DRAM, and the like is important. One of the techniques is a wet etching using a chemical liquid. For example, in the production of a circuit wiring in a microscopic transistor circuit and a substrate having a metal electrode material, a precise etching processing is required. Further, the same is true on the production of an electrode structure in the capacitor structure of the above-mentioned DRAM. However, adequate studies have not yet done on the conditions and chemical liquids for selectively etching each layer applied to a substrate having a metal electrode or the like.
There are examples of the studies made on chemical liquids for etching silicon oxides that constitute a device substrate. For example, Patent Literature 1 proposes a method of efficiently etching a thermally-oxidized film of a silicon wafer by using hydrofluoric acid and ammonium fluoride.